title: Novel Fe3+-Based1H MRIβ-Galactosidase Reporter Molecules**
abstract: There is increasing interest in the development of reporter agents to reveal enzyme activityin vivousing small animal imaging. We have previously demonstrated the feasibility of detectinglacZgene activity using the commercially available 3,4-cyclohexenoesculetin-β-D-galactopyranoside (S-Gal™) as a1H MRI reporter. Specifically, β-galactosidase (β-gal) releases the aglycone, which forms an MR contrast-inducing paramagnetic precipitate in the presence of Fe3+. Contrast was primarily T2-weighted signal loss, but T1effects were also observed. Since T1-contrast generally provides signal enhancement as opposed to loss, it appeared attractive to explore whether analogues could be generated with enhanced characteristics. We now report the design and successful synthesis of novel analogues together with characterization of1H MRI contrast based on bothT1andT2response to β-gal activityin vitrofor the lead agent.
authors.affiliation: Department of Radiology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390-9058, USA.
authors.forename: Jian-Xin
authors.initials: JX
authors.lastname: Yu
authors.forename: Praveen K
authors.initials: PK
authors.lastname: Gulaka
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Vikram D
authors.initials: VD
authors.lastname: Kodibagkar
authors.forename: Ralph P
authors.initials: RP
authors.lastname: Mason
keywords: NMR; enzyme; hydrolases; relaxivity; reporter molecules